experimental and theoretical investigation for the improvement … · 2014-06-27 · abstract— in...

Abstract— In the present study , an experimental and

theoretical investigation has carried out to study the

enhancement of lift on NACA 0012 airfoil as well as lift to

drag ratio by adding some of high lift devices. . It includes the

enhancement of the lift of the airfoil by using three types of

high lift devices. The experiment was executed by using a

wind tunnel with Reynolds number equals to 2.7×105 based on

the chord line length of the airfoil. In the experimental work

the test was carried out for the base line airfoil only for angles

of attack 0°,4°,8°,12°, 16° The theoretical study was executed

using CFD package which is ANSYS FLOTRAN 12.1 by

using CAD preparation of two dimensional NACA 0012

airfoil. The study investigates adding a Gurney flap with two

different heights 2% c and 3% c, extended flaps with two

different lengths and deflection angles, using 2% c extended

flap with deflection angles equals 0° and 5°, 4% c extended

flap with deflections angles equals 5°. A 3% c T flap was also

added. To show the effect of the cavity in front of gurney flap,

a 3% c closed flap or filled in flap was added to the airfoil and

compared with the same height of Gurney flap. a good

improvement in lift coefficient for gurney flap and extended

flaps was obtained . The best results that could be achieved

using Gurney flap was found to be with height = 2% .The best

results that could be achieved using static extended trailing

edge was found with height 4% C and deflection angle

=5°because it has larger lift to drag ratio. Lift coefficient of

closed flap was half of that obtained by Gurney flap.

Keywords— Aerodynamic Characteristic of NACA 0012 airfoil

I. INTRODUCTION

N recent years there has been an increased interest in

primary criteria in the design of wings include maximizing

efficiency and control; that is, increasing desired effects

(e.g. lift) while diminishing undesired effects (e.g. drag) so

that the airfoil becomes more functional and provides

sufficient means of control. High-lift aerodynamics continues

playing an important role in the design of a new aircraft.

Improved high lift performance can lead to increase range and

imad Windi is with the Babylon University, College of Engineering,

Mechanical Engineering Department, Babil, Iraq (corresponding author’s

phone:+964 7806581769; e-mail: [email protected]).

payload, or decrease landing speed and field length

requirements. Hence, there is a continuous need for improving

the maximum lift and lift-to-drag ratio, L/D.

The Gurney Flap is named after American aero dynamist Dan

Gurney who introduced in the form of a vertical tab attached to

the trailing edge of an ordinary aerofoil. Usually, his use on

the racing car wing is intended to keep a racing car on the road

it improving wing efficiency. It is a simple length of aluminum

or carbon fiber right-angle rigidly bolted, riveted on the

pressure side perpendicular to the chord as shown Fig (1)

Fig. 1 Isometric airfoil with gurney flap

Extended flaps is thin splitting plate mounted at the trailing

edge of an airfoil, but rather than protruding 90° to the chord

line, it is mounted with a small deflection angle (5°-10°) figure

(2).

Fig. 2 Extended flap

A two Gurney flaps attached to both the upper and lower

surfaces of the airfoil making the modification as same as T

letter, therefore it is called T flab.

The study on Gurney flap was first reported by Liebeck,

,(1978), [1] who conducted the experiment for a Newman

symmetric aerofoil with a 1.25% c Gurney flap in a wind

tunnel. In comparison with the aerofoil without the Gurney

flap, Gurney flap increased the lift coefficient and maximum

lift coefficient greatly; meanwhile, the meanwhile, the zero lift

angle-of-attack and drag of the aerofoil were reduced. Liebeck

also proposed the existence of a separation bubble upstream of

the Gurney flap, and the presence of two counter- rotating

vortices just downstream of the Gurney flap.

Wadcock, (1987), [2], performed wind tunnel tests at a

Reynolds Number of 1.64 × 10^6 on a baseline NACA 4412

airfoil. These tests showed a significant increase in the lift

coefficient, shifting the lift curve up by 0.3 for a Gurney flap

of 1.25% of the chord length, and providing a greater

maximum lift. There was no appreciable increase in drag until

Experimental and Theoretical Investigation

for the Improvement of the Aerodynamic

Characteristic of NACA 0012 airfoil

Imad Shukri Windi, Mawlood Anwer Faris, and Hanan Kareem

I

International Journal of Mining, Metallurgy & Mechanical Engineering (IJMMME) Volume 2, Issue 1 (2014) ISSN 2320–4060 (Online)

11

mailto:[email protected]

the Gurney flap was extended beyond about 2% of the airfoil

chord length, at which point the flap extended beyond the

boundary layer thickness.

Giguere, P. et al, (1995),[3]. Quantified the effects of

Gurney flaps with respect to their height scaled to the

thickness of the boundary layer. Using this scaling, it is

observed that Gurney flaps are effective when the heights are

at the same scale as the boundary layer; when the boundary

layer is significantly thicker, there is essentially no effect.

Wang et al (2006), [4] studied the Gurney flap on a swept

wing model at Mach numbers ranging from 0.05 to 0.7 through

force measurements. The largest increments of the maximum

lift coefficient and maximum lift- to-drag ratio were 16.8 and

24.1%, respectively

The experimental and computational study performed by

Ross et al, ( 1995), [5], to determine the effect of Gurney flaps

on two-element NACA 632-215 Mod B airfoil. Jang et. al.(

1992), [6] used an incompressible Navier-Stokes code to

compute flow field about NACA 4412 airfoil with Gurney flap

heights ranging from 0.5% to 3% of chord.

II. EXPERIMENTAL SETUP

The experiment was conducted in the low speed wind tunnel

an open circuit type figure (3). The testes were performed at a

free stream velocity of 29m/s Providing Reynolds number, Re

=2.7× 105 based on the airfoil chord.

Fig. 3 airfoil inside the wind tunnel

The airfoil shape chosen for this work was the NACA0012,

airfoil which has zero camber, and its maximum thickness is

12% of the chord at the quarter-chord location. NACA0012

airfoil used in this experiment had a chord length of 0.152 m,

and span (b) of 460 mm.

III. THEORETICAL STUDY

The CFD analysis in the present study can be used to

simulate the flow around a NACA 0012 airfoil model and

explain the effects of the different types of flaps on the

enhancement of the lift on airfoil. In the present study the CFD

program was ANSYS12.1 by using FLOTR CFD simulation

with Reynolds No. equals to 2.7* based on the chord line

of the airfoil. c is the chord length, x is the position along the

chord from 0 to c, and is the maximum thickness as a

fraction of the chord. Mapped mesh was used figure (4).

Fig. 4 mesh generation

The boundary domain is enclosed by the wind tunnel walls

of the closed test section some reasonable.

IV. RESULT AND DISCUSSION

The lift and drag coefficients of the airfoil at different angle

of attack. Figure (5) shows the lift and drag coefficient for the

airfoil with different sizes of Gurney flap. Gurney flap

substantially increase the maximum lift coefficient by 32.89%

and 39.42% for 2%c and 3%c Gurney flap respectively

Consequently, the stall angle slightly degreased from 12° to

10° for both sizes of Gurney. Figure (6) shows the lift

coefficient as a function of angle of attack for the model with

extended flap, According to this figure, the CL distribution is

shifted up and the lift is enhanced depending on the deflection

angle and relative length of extended flap. . Figure (7) show

the effect of closed flap on the lift coefficient. This figure

shows an increase in lift coefficient of approximately 16.5%,

which is slightly less than the 2% flap case. This result seems

reasonable since the rear point of the camber line is effectively

the same for these two cases, though the camber lines

themselves are not the same.. The effect of T strip on the

baseline wing lift curve is shown below in Figure (8). T-strips

produced an increase in maximum lift coefficient. However, T-

strips produced no shift in the wing zero-lift angle of attack

because the flow field is symmetric, in another word, the upper

half of the T effectively canceling the effect of the lower half.

Figure (17) show the stream line of the airfoil with 3% c

Gurney flap and figure (18) show the velocity vector of the

same Gurney flap. At zero angle of attack, two counter-

rotating vortices of similar strength are visible aft of the

Gurney flap. As angles of attack increase, a recirculation

region and retarded flow can be seen on the airfoil lower

surface, at the front face of the Gurney flap and the vortex near

the airfoil upper (suction) surface becomes dominate. This

flow field agrees with that hypothesized by Liebeck [1]

V. CONCLUSION

The presence of a Gurney flap on an airfoil served to

increase the lift generated on the body. As the height of the

Gurney flap was increased, the lift also increased with small

drag penalty. The zero lift angles degrease. The best results

that could be achieved using Gurney flap was found to be with

height = 2% c because it gave lift to drag ratio higher than

Gurney flap 3% c. In general, Gurney flaps are not suitable for

cruise flight due to the reduced lift to drag ratio by the larger

drag penalty at lower lift coefficients. Adding 3% T _Gurney

flap reduces the lift and increase drag with compared with

airfoil with 3% c Gurney flap. Therefore the lift to drag ratio

was less than 3% c Gurney flap. Airfoil with closed flap

generated approximately half the lift increment of the open-

cavity case. Thus, it appears that a significant part of the lift


12

increment produced by the Gurney flap results directly from

the upstream shedding and its influence on the trailing wake.

The best results that could be achieved using static extended

trailing edge was found with height 4% c and deflection angle

=5°because it has larger lift to drag ratio. Static extended

trailing edge flap can be used in cruise flight because it has a

good potential to improve the cruise flight efficiency.

0 2 4 6 8 10 12 14 16

Angle of attack

0

0.4

0.8

1.2

1.6

CL

baseline airfoil

airfoil with 2%c GF

airfoil with 3%c GF

Fig. 5 Lift coefficient versus AOA for various heights of

Gurney flap

0 2 4 6 8 10 12 14 16

Angle of attack

0

0.2

0.4

0.6

0.8

1

1.2

CL

baseline airfoil

SETE 2% c, delta = 0 deg.

SETE 4% c ,delta = 5 deg.

SETE 2% c, delta = 5 deg.

Fig. 6 Lift coefficient versus AOA for various heights and

deflection angles of ext. flap

0 2 4 6 8 10 12 14 16

Angle of attack

0

0.4

0.8

1.2

1.6

CL

baseline airfoil

closed flap

2% c GF

3% c GF

Fig. 7 Lift coefficient versus AOA for Gurney flap included

closed flap

0 2 4 6 8 10 12 14 16

Angle of attack

0

0.2

0.4

0.6

0.8

1

1.2

1.4

CL

baseline airfoil

3% c T flap

3% c GF

Fig. 8 Lift coefficient versus AOA for T Gurney flap


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Fig. 9 Stream lines of NACA 0012 Airfoil with 3% c Gurney flap

Fig. 10 Velocity Vector of NACA 0012 Airfoil with 3% c Gurney

flap


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REFERENCES

[1] [1] Liebeck R (1978), “Design of subsonic airfoils for high lift.” Journal

of Aircraft 15(9), pp. 547-61

[2] [2]Wadcock A.,(1987) "Investigation of Low-Speed Turbulent

Separated Flow Around Airfoils". NASA Contractor Report No.

177450, 1987

[3] [3]Giguere P, Lemay J, Dumas G,(1995) "Gurney Flap Effects and

Scaling for Low Speed Airfoils," AIAA Paper 95-1881, 13th AIAA

Applied Aerodynamics Conference San Diego, June 1995

[4] [4]Wang. J. J, Zhan J. X., Zhang W, Wu Z (2006)“Application of a

Gurney Flap on a Simplified Forward Swept Aircraft Model"Journal of

Aircraft, 43(5), pp 1561-16

[5] [5]Ross J. C., Storms, B. L. and Carrannanto, P. G., (1995)“Lift

Enhancing Tabs on Multi element Airfoils,” Journal of Aircraft, Vol. 32,

1995, pp. 64

[6] [6]Jang, C.S., Ross, J. C., and Cummings, R. M.,(1992) “Computational

Evaluation of an Airfoil with a Gurney Flap,” AIAA Paper 92-2708

[7] [7]Pope, A. Harper, J, J, (1966) "Low Speed Wind Tunnel Testing" John

Wiley and Sons, New York.

[8] [8]Estman Jacob 1930

[9] [9]Yoo Neung-Soo,(2000)" Effect of the Gurney Flap on a NACA

23012 Airfoil" KSME International Journal, Vol. 14, No.9, pp. 1013-

10190.

[10] [10]Ferzigen, J. H. and Peric, M (1999)."Computational methods for

Fluiddynamic".2thedition, Springer Berlin,

[11] [11]ANSYS Fluids Analysis Guide, ANSYS Release 12.1, ANSYS Ins.

Is a UL, Registered ISO 9001: 2000 Company, November 2004.


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experimental and theoretical investigation for the improvement … · 2014-06-27 · abstract— in...

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